The purposes of this research project are: 1) to test the ability of a gravity model to describe and to predict patient flows in hospital markets, 2) to compare "socioeconomic distance" with physical distance as determinants of flows and 3) to examine the effects of inner-city hospital closures on access to services by lower-income patients. This project will estimate gravity models of patient flows in the Chicago, IL hospital service market. Geographic submarkets (West and South sides of Chicago) and markets determined by major clinical service categories (i.e. obstetrics, surgery, medicine, pediatrics and psychiatry) also will be evaluated. Gravity models that describe patient flows in these areas for a base period (the first six months of 1987) will be constructed and calibrated. These models will incorporate key physician, hospital, demographic and other factors important in determining patient flows, as well as origin-destination separation factors (e.g. travel time, distance) traditionally found in gravity models. An index of socioeconomic distance will be added to the model. These gravity models then will be used to predict patient flows in the markets for a future time period (first six months of 1990) and the results compared to actual flows for the period. Model predictions specifically will address the closure of nine Chicago hospitals during the study period (1987-90). In addition, some hospitals expanded or eliminated service offerings and the State of Illinois' Medicaid program began contracting with selected hospitals to provide services to its beneficiaries. The ability of the gravity models to predict future patient flows will be tested. Finally, hospital closures, along with changes in service mix and new payment policies, caused a reallocation of patient flows to other hospitals in the market. The extent to which access to hospital services by lower-income patients may be adversely affected by hospital closures will be analyzed. Selected public policies, e.g. public hospital bed relocations and hospital subsidies, that could affect future patient flows also will be evaluated.